Waterborne basecoat compositions for use in basecoat/clearcoat applications

ABSTRACT

Compositions containing polyurethane dispersions and water reducible resins particularly suited for use as basecoats in low VOC basecoat/clearcoat vehicle coatings.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.08/973,724, filed on Dec. 23, 1998, now U.S. Pat. No. 6,057,400, whichis based on International Application No. PCT/US96/09519, filed on Jun.6, 1996, which claims priority from U.S. patent application Ser. Nos.08/472,449, 08/485,890, 08/475,151, and 08/479,070, all of which werefiled on Jun. 7, 1995, and all of which are now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to waterborne basecoat compositions havingparticular utility in multi-layer coatings such as vehiclebasecoat/clearcoat (BC/CC) applications. The basecoat compositions ofthis invention can be used in either original equipment manufacturer(OEM) production lines or in automotive vehicle refinish (VR) body shopsand the like.

Multi-layer coatings for use over the surface of automobiles, trucks andthe like have been in use for years. Originally, such coating systemsused organic solvents. As environmental concerns and regulations becamemore prevalent, such organic solvent-based systems fell out of favor. Inrecent years, the development of waterbome systems has increased. Inparticular, the development of waterborne basecoats as part of avolatile organic content (VOC) compliant basecoat/clearcoat system hasincreased. Many of the world's large coatings companies have disclosedwaterborne basecoats for use in basecoat/clearcoat vehicle coatings. Byway of example, BASF, DuPont, ICI and PPG all have patents in this area:U.S. Pat. No. 5,204,401 (Anderson et al., BASF) teaches metallic andnonmetallic waterborne basecoats having a water-reducible acrylic resinwith nonionic and acid functionality derived from vinyl monomers havingnonionic and urethane functionality. U.S. Pat. No. 5,169,719 (BalatanBASF) teaches water-dilutable polyurethane/acrylic copolymers useful asthe principal resin and as pigment grind resins in waterborne automotivebasecoats. U.S. Pat. No. 5,157,069 (Campbell, BASF) teaches an aqueouscoating comprising a nonionic dispersion of a polymer selected from thegroup consisting of acrylic resin, polyurethane resin (and mixturesthereof) with a nonionic water soluble rheology control polymer (such asa polyether, cellulose, cellulose derivative, polyvinylalcohol, etc.)and pigments. U.S. Pat. No. 5,066,732 (Savino et al., BASF) teacheswater dispersible nonionic polyurethane resins having polyetherbackbones. U.S. Pat. No. 5,017,673 (Balatan, BASF) teaches waterdispersible nonionic polyurethane resins having polyester backbones.U.S. Pat. No. 4,978,708 (Fowler et al., BASF) teaches an aqueousbasecoat containing an anionic polyurethane resin and an anionic acrylicpigment grind resin. U.S. Pat. Nos. 4,558,090 and 4,489,135 (Drexler etal., BASF) teach a process and composition useful as a basecoat in amultilayer coating wherein the basecoat is an aqueous polyurethane. U.S.Pat. No. 5,204,404 (Werner Jr., et al., DuPont) teaches waterbasedcoating compositions containing an acrylic silane polymer and apolyurethane polymer. U.S. Pat. No. 5,051,464 (Johnson et al., DuPont)teaches a waterbased coating composition containing an acrylourethanepigment dispersing polymer and a binder. U.S. Pat. Nos. 5,006,413 and4,954,559 (Den Hartog et al., DuPont) teach waterbased coatingcompositions containing a methylol (meth)acrylamide acrylic polymerbinder and a polyurethane. U.S. Pat. No. 5,100,735 (Chang, DuPont)teaches an improved process for forming a multilayer finish on anautomobile comprising using a waterborne acrylic basecoat and a highsolids, solvent-based acrylic, polyester, or polyesterurethane clearcoatwith an alkylated melamine formaldehyde crosslinking agent. U.S. Pat.No. 4,403,003 (Backhouse, ICI) teaches a process for producing amultilayer coating wherein an aqueous dispersion pigmented basecoatcontaining crosslinked microparticles is first applied. U.S. Pat. No.4,822,685 (Perez et al., PPG) teaches a method of forming a multilayercoating over a substrate wherein an aqueous-based polyurethanedispersion is used as a pigmented basecoat. U.S. Pat. No. 4,719,132(Porter Jr., BASF) teaches an aqueous basecoat comprising an aqueouspolyurethane resin.

SUMMARY OF THE INVENTION

The present invention relates to a waterborne basecoat compositionwhich, together with an appropriate clearcoat composition, isparticularly useful as a multilayer coating system for use in both OEMand VR applications. The basecoat composition is low in VOC and can bepigmented with a broad range of pigments readily available and used inthe automotive industry, including nonmetallic pigments, metallicpigments and other opalescent pigments. It is specifically designed tohave good solvent and water resistance. This prevents basecoat attackand degradation by the clearcoat or topcoat and promotes clearcoat glossand metal stability and orientation for metallic pigments. Yet, thebasecoat also remains easy to clean from spraying equipment.

The waterborne basecoat composition of the present invention comprises:

a. water,

b. a polyurethane resin dispersible in water,

c. one or more resins selected from the group consisting ofwater-reducible resins and aqueous emulsion polymers, produced by afree-radical addition polymerization reaction, and

d. pigment.

In a preferred embodiment, the waterborne basecoat composition of thepresent invention is obtained by mixing two main components prior toapplication to the substrate:

a. one or more pigmented toner resin components, and

b. a mixing clear resin component.

In such an embodiment, each pigmented toner resin component compriseswater, a resin or polymer and pigmentation for the basecoat. It shouldbe appreciated that many of today's popular basecoat colors are theresult of a combination of two or more pigmented toner resins. Eachtoner resin comprises one or more resins or polymers selected from thegroup consisting of i) polyurethane resins dispersible in water, ii)water-reducible resins and aqueous emulsion polymers, produced by afree-radical addition polymerization reaction, and mixtures thereof.Pigments in the toner resin component comprise standard pigments such astitanium dioxide, carbon black, red oxide and the like, opalescentpigments such as micas, and metallic pigments such as aluminums.Generally, such pigments are available in the form of pigmentdispersions; however, powdered pigments are also available and useful.The combination of one or more such toner resins provides the OEMpainter or the VR refinisher with the desired basecoat color. A methodfor properly selecting the types of resins to be used in the tonercomponents is taught herein.

In the above-mentioned preferred embodiment, the mixing clear resincomponent comprises:

a. one or more aqueous emulsion polymers produced by a free-radicaladdition polymerization reaction (particularly useful in the case ofambient cure, or forced air dry cure systems such as those used invehicle refinish shops), or

b. a polyurethane dispersion resin in combination with a small amount ofaqueous emulsion polymer (particularly useful in the case of temperaturecured or bake dry systems such as those used in OEM production lines).

Preferred basecoat ingredients are more fully described below. Inaddition, the criteria for determining the requisite combinations ofpigment and resin in each preferred component are described in moredetail.

Accordingly, it is an object of this invention to teach a novelwaterborne basecoat composition particularly useful in multi-layerbasecoat/clearcoat applications.

It is a further object of this invention to teach a multi-layer coatedsubstrate wherein the basecoat layer comprises the novel waterbornebasecoat described herein.

It is yet a further object of this invention to teach a process forcoating a substrate with a multi-layer coating composition comprisingthe novel waterborne basecoat described herein.

These and other objects will become more apparent from the detaileddescription of the invention below.

DETAILED DESCRIPTION OF THE INVENTION

As described briefly above, the present invention relates to awaterborne basecoat composition which, together with an appropriateclearcoat composition, is particularly useful as a multilayer coatingsystem for use in both OEM and VR applications. The basecoat compositionis low in VOC and can be pigmented with a broad range of pigmentsreadily available and used in the automotive industry, includingnonmetallic pigments, metallic pigments and other opalescent pigments.

The waterbome basecoat composition of the present invention comprises:

a. water,

b. a polyurethane resin dispersible in water,

c. one or more resins selected from the group consisting ofwater-reducible resins and aqueous emulsion polymers, produced by afree-radical addition polymerization reaction, and

d. pigment.

In a preferred embodiment, the waterborne basecoat composition of thepresent invention is obtained by mixing two main components prior toapplication to the substrate:

a. one or more pigmented toner resin components, and

b. a mixing clear resin component.

It should be appreciated that many of today's popular basecoat colorsare the result of a combination or mixture of two or more pigmentedtoner resins. Each such pigmented toner resin component comprises water,a resin or polymer and pigmentation for the basecoat. In the presentinvention, each toner resin comprises one or more resins selected fromthe group consisting of i) polyurethane resins dispersible in water, ii)water-reducible resins and aqueous emulsion polymers, produced by afree-radical addition polymerization reaction, and mixtures thereof.Pigments in the toner resin component comprise standard pigments such astitanium dioxide, carbon black, red oxide and the like, opalescentpigments such as micas, and metallic pigments such as aluminums. Themixture of one or more such toner resins, together with the mixing clearcomponent, provides the OEM painter or the VR refinisher with thedesired basecoat color. A method for properly selecting the types ofresins to be used in the toner components is taught herein.

In the above-mentioned preferred embodiment, the mixing clear resincomponent comprises:

a. one or more aqueous emulsion polymer resins produced by afree-radical addition polymerization reaction (particularly useful inthe case of ambient cure, or forced air dry cure systems such as thoseused in vehicle refinish shops), or

b. a polyurethane dispersion resin in combination with a small amount ofaqueous emulsion polymer (particularly useful in the case of temperaturecured systems such as those used in OEM production lines).

The detailed discussion below first describes each of the criticalingredients in compositional detail. The discussion then proceeds todescribe the preferred combinations of ingredients as well as a recipefor determining which various compositions to use when formulatingpreferred components. Throughout the detailed discussion, embodiments ofthis invention are exemplified. It should be appreciated that manydifferent combinations of the critical ingredients may arrive atbasecoat compositions which perform suitably. However, it should also beappreciated that not all of such combinations would also exhibit theancillary (but important) criteria for being considered useful in acommercial setting. For example, one might simply combine each of thecritical ingredients in the amounts described herein to arrive at asingle basecoat composition that is particularly well suited for asingle painting job; however, such composition might not be sufficientlyflexible to be stocked at a vehicle refinisher's shop to be used in thebroad range of situations that face the refinisher. In such a situation,the preferred embodiments referred to above and in more detail hereinhave their greatest utility.

Basecoat Compositional Requirements

a. Basecoat Resins

The basecoat of the present invention utilizes three basic resins invarious combinations. The first resin, which is present in everyembodiment of the basecoat, is a water-dispersible polyurethane resin.Preferably, the polyurethane dispersion resin contains no organicsolvent and will dry by evaporation of any water used to disperse theresin to yield a tough, flexible film having good abrasion resistance,ultraviolet light stability, water and chemical resistance.

A preferred polyurethane resin is typically a dispersion in water of thereaction product of at least one polyol, preferably selected from thegroup consisting of:

1) polyols such as the saturated and unsaturated polyhydric alcoholsincluding ethylene glycol, propylene glycol, neopentyl glycol,1,4-butanediol, 1,4-butenediol, 1,6-hexanediol, furan dimethanol, andcyclohexane dimethanol;

2) polyester polyols formed from the reaction of saturated andunsaturated polyhydric alcohols such as ethylene glycol, propyleneglycol, neopentyl glycol, 1,4-butanediol, 1,4-butenediol,1,6-hexanediol, furan dimethanol, and cyclohexane dimethanol, withsaturated and unsaturated polycarboxylic acids and derivatives thereofsuch as maleic acid, fumaric acid, itaconic acid, succinic acid,glutaric acid, adipic acid, isophthalic acid, terephthalic acid,phthalic anhydride, dimethyl terephthalate, dimer acids and the like;

3) polyesters formed by the reaction of lactones, such as caprolactone,with a polyol;

4) polyether polyols such as the products of the polymerization of acyclic oxide such as ethylene oxide, propylene oxide or tetrahydrofuran;

5) polyether polyols formed by the addition of one or more cyclic oxidesto water, ethylene glycol, propylene glycol, diethylene glycol,cyclohexane dimethanol, glycerol, or Bisphenol A;

6) polycarbonate polyols such as the reaction product of1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol ortetraethylene glycol with diaryl carbonates such as diphenyl carbonateor phosgene;

7) polyacetal polyols such as the reaction product of a glycol such asdiethylene glycol, triethylene glycol or hexanediol with formaldehyde;

8) polyols such as dihydroxyalkanoic acids including dimethylolpropionicacid; and mixtures thereof, with an isocyanate composition.

Preferably, the polyols are predominantly di-functional. However,higher-functional alcohols can also be included. The most preferredpolyols are a combination of 1) polyether polyols such as the productsof the polymerization of a cyclic oxide such as ethylene oxide,propylene oxide or tetrahydrofuran; and 2) a polyol containinghydrophilic groups. A particularly preferred polyol containinghydrophilic groups is dimethylolpropionic acid.

Optionally, and generally present during the reaction is up to about0.06%, preferably between about 0.01% and about 0.04% (by weight basedupon total solids of polyol and isocyanate) of a catalyst such asdi-butyl tin dilaurate, tin octoate and the like.

To ensure that the intermediate is dispersible in an aqueous media,generally a percentage of the total polymer weight solids, preferablybetween about 1% and about 10%, is contributed by polyols(or othercompositions having active hydrogen atoms or the ability to react withisocyanates, such as amines or mercaptans) having the ability tocontribute ionic or hydrophilic groups to the polyurethane-urea; forexample, polyols, amines or mercaptans containing carboxylic acidgroups, sulfonic acid groups, phosphoric acid groups, ammonium salts,phosphonium salts or sulfonium salts. Acceptable polyols, amines and thelike are described at Column 10, lines 18-69 of U.S. Pat. No. 4,880,867,which portion of said patent is incorporated herein by reference.

In a typical reaction mechanism, the polyol is charged with the catalystto a reaction vessel, and the contents are heated to a temperature ofbetween about 70° C. and about 100° C., with continuous or stepwiseaddition over a period of time, preferably between about ½ hour to about4 hours, of the isocyanate-functional materials.

It should be appreciated that from a chemistry standpoint, organicsolvents are acceptably included in the composition. However, thisinvention relates to low or zero VOC dispersions, and, consequently,inclusion of such solvents in large percentages is considered outsidethe scope of the invention. Such solvents typically include n-methylpyrolidinone, dimethyl formamide, methyl ethyl ketone, toluene, andmixtures thereof. After complete addition of the isocyanate materials,the reaction vessel temperature is generally maintained between about80° C. and 100° C. for so long as necessary to bring the residualisocyanate percentage (based upon the total solids weight of thepolymer) below about 8.0%, preferably into a range between about 1.5% toabout 6.0%. This takes approximately 2 to 4 hours. Residual isocyanatepercentage can be measured by any means well known in the art. Thecontents are then generally cooled to below about 70° C. and the ionicgroups present in the product of the above reaction are then neutralizedby the addition of a weak base, such as triethylamine, trimethylamine,triisopropyl amine, tributyl amine, N,N-dimethyl-cyclohexyl amine,N,N-dimethylstearyl amine, N,N-dimethyl aniline, N-methylmorpholine,N-ethylmorpholine, N-methylpiperazine, N-methylpyrolidine,N-methylpiperidine, N,N-dimethyl-ethanol amine, N,N-diethyl-ethanolamine, triethanol amine, N-methyldiethanol amine, dimethylaminopropanol,2-methoxyethyldimethyl amine, N-hydroxyethylpiperazine,2-(2-dimethylaminoethoxy)-ethanol and 5-diethylamino-2-pentanone andmixtures thereof. Most preferred neutralization agents are the tertiaryamines as they are not reactive with the free isocyanate groups.Particulary preferred is triethylamine. The weak base can be added inexcess, that is, an amount greater than that necessary to neutralize theionic groups; however, too much weak base will cause an unacceptableincrease in the VOC of the composition. At a minimum, the amount of weakbase added should be sufficient to neutralize at least about 80% of theionic groups present in solution. Preferably, the weak base is added inan amount sufficient to theoretically neutralize 100% of the ionicgroups.

The intermediate is then dispersed in water. The percentage of solids inthe water can range up to about 60% by weight, preferably between about20% to 50% by weight. A difunctional amine compound such as ethylenediamine, propylene diamine, butylene diamine, hexamethylene diamine,cyclohexylene diamine, piperazine, hydrazine, mixtures thereof,equivalents thereof and the like in an amount sufficient to react withup to about 90% of the theoretical amount of residual iocyanatefunctionality can optionally be included in the dispersing media forchain extension of the polyurethane. Chain extenders having afunctionality greater than two should not be included in any appreciableamount due to their tendency to cause unacceptably high levels ofbranching.

The isocyanate-functional material is selected from materials which arewell known in the art and include the mono-, di-, tri- andmulti-functional isocyanates. Di- and tri-functional isocyanates aremost preferred.

Suitable isocyanate functional materials include aromatic,cycloaliphatic and aliphatic isocyanates such as cyclohexyl isocyanate,phenyl isocyanate, toluene isocyanate, hexamethylene diisocyanate,4,4′-dicyclohexylmethane diisocyanate, 1,4-tetramethylene diisocyanate,1,10-decamethylene diisocyanate, toluene-2,4- or 2,6-diisocyanate,1,5-naphthalene diisocyanate, 4-methoxy-1,3-phenylene diisocyanate,benzene 1,3-bis (1-isocyanato-1-methylethyl), 4-chloro-1,3-phenylenediisocyanate, 2,4′-diisocyanatodiphenyl ether,5,6-dimethyl-1,3-phenylene diisocyanate, 2,4-dimethyl-1,3-phenylenediisocyanate, 4,4′-diisocyanatodiphenylether, benzidine diisocyanate,4,4′-diisocyanatodibenzyl, methylene-bis(4-phenyl-isocyanate),1,3-phenylene diisocyanate, 1,2,4-benzene triisocyanate andpolymethylene polyphenyl isocyanate.

Most preferred is isophorone diisocyanate.

Of the commercially available polyurethane dispersions, the NeoRezR-966® polyurethane resin available from Zeneca Resins is particularlypreferred. It is a colloidal dispersion of an aliphatic urethane inwater. Analysis of this dispersion shows it to comprise the reactionproduct of isophorone diisocyanate, polytetrahydrofuran(HO—[—(CH₂)₄—O—]_(n)—H) of molecular weight M_(w), approximately 1600,and dimethylolpropionic acid.

As discussed above, the basecoat composition also comprises one or moreresins or polymers selected from the group consisting of water-reducibleresins and aqueous emulsion polymers, produced by a free-radicaladdition polymerization reaction. It should be appreciated that it isoften unclear as to whether a particular resin, when put into water, isa solution or dispersion. For purposes of this invention it is notnecessary to determine if a resin is actually a water-reducible solutionpolymer or an aqueous dispersion provided that such resin meets thecompositional requirements described herein.

The monomers useful in preparing either type of resin are generallyselected from the group consisting of acrylic and vinyl monomers whichwould produce a polymer via the free radical addition reactionmechanism. The resultant polymer is either stably insoluble in theaqueous polymerization medium (i.e. a dispersion) or soluble in theaqueous polymerization medium (i.e. a solution polymer). Suitablemonomers are selected from the group consisting of acrylonitrile,methacrylonitrile, hydroxy ethyl acrylate and methacrylate, methylacrylate and methacrylate, hydroxy propyl acrylate and methacrylate,ethyl acrylate and methacrylate, butyl acrylate and methacrylate, laurylacrylate and methacrylate, trimethylol propane triacrylate andtrimethacrylate, hexanediol diacrylate, caprolactone modified hydroxyethyl acrylate, polyethylene oxide acrylate and methacrylate,polypropylene oxide acrylate and methacrylate, allyl alcohol,acrylamide, methacrylamide, vinyl chloride, vinylidene chloride, acrylicacid, methacrylic acid, itaconic acid, maleic acid, fumaric acid,styrene, divinyl benzene, vinyl naphthalene, vinyl toluene, the methylesters of itaconic, maleic and fumaric acid, and mixtures thereof.

In addition to pure monomers, preformed polymers, polymericintermediates, multifunctional epoxides, melamines and isocyanates, canbe included in the reactor charge.

One preferred resin (hereinafter referred to as Dispersion Resin #1) isa low molecular weight 65% solids (by weight) water-reducible resinprepared by free-radical addition polymerization in 2-butoxy ethanolusing t-butyl peroctoate as initiator of between about 5-15% methylmethacrylate, about 5-15% styrene, about 10-20% butyl acrylate, about35-45% butyl methacrylate, about 10-20% hydroxy ethyl methacrylate andabout 5-10% acrylic acid, all monomer percentages by weight of totalmonomer added. Acid value is generally between about 40 and about 75,preferably between about 50 and about 65. The techniques used to preparesuch suitable resins are well-known in the art. In general, standardfree radical polymerization techniques are acceptable. One suchprocedure comprises a four hour addition of monomers and free radicaladdition initiator to a reactor containing solvent at a temperature ofbetween about 100 degrees C. and about 120 degrees C. followed by a 15minute chase of additional initiator and an additional two hour holdtime at the same temperature.

An additional preferred polymer is an aqueous emulsion polymercommercially available from Rohm & Haas under the tradename RhoplexWL-91™. Rhoplex WL-91 is a thermoplastic acrylic emulsion sold at 41.5%solids by weight in water. This polymer has been analyzed asapproximately 50% styrene (by weight of total monomers), approximately34% 2-ethylhexyl acrylate, approximately 4% acrylic acid andapproximately 12% acrylonitrile.

Preferred Embodiments

In a preferred embodiment, the basecoat composition is not merely amixture of the above-identified ingredients. Rather, it comprises twomain components: one or more pigmented toner resin components and amixing clear resin component. This arrangement is preferred as it givesthe painter the flexibility to mix one or more compatible pigmentedtoners together to formulate to a specific color and use the mixingclear component to adjust the tint strength of the final basecoat. Thisformulation flexibility is essential in vehicle refinish shops. Each ofthe preferred embodiment components is described in more detail below.

a. Toners

We have found that because of the differences in standard nonmetallicpigments and the metallic and mica-based pigments, differentcombinations of resins are useful depending on the pigmentation of thebasecoat. For example, if preparing a green flop blue toner using onlynonmetallic and non-mica-based pigments, the toner can be prepared bymaking a grind paste comprising the ingredients in Table 1:

TABLE 1 Ingredient # PoundsGallons Description 1 584.4 70.4 DeionizedWater 2 7.2 1.0 Dimethyl ethanol amine 3 141.9 16.7 Dispersion Resin #14 183.4 12.0 Blue Pigment

The procedure for making the grind paste is to premix ingredients #1through #3 for 20 minutes at low rpm using a high speed disperser.Slowly add ingredient #4 and stir for another 20 minutes. Charge theslurry to a stainless steel ball mill and process for 72 hours to aHegman grind of 7+. Letdown the grind paste with the letdown formulashown in Table 2:

TABLE 2 Ingredient # PoundsGallons Description 1 552.7 64.3 NeoRez R-9662 275.7 30.1 Grind Paste from Table 1 3 12.3 1.5 Deionized Water 4 13.81.6 Diethylene glycol methyl ether 5 10.5 1.2 Acrysol RM-8 RheologyModifier 6 2.2 0.3 Surfynol ™ 104E Surfactant 7 9.4 1.1 Deionized Water

The letdown procedure is to add ingredient #2 to ingredient #1 slowlywith good agitation. Thoroughly mix ingredients #3 through #6 and thenadd with good agitation. Add #7 to adjust viscosity to 2400-3600 cpsusing a Brookfield LVT #3 spindle at 30 rpm.

On the other hand, to prepare a metallic toner, we have found that it ispreferred to create an intermediate comprising the ingredients of Table3:

TABLE 3 Ingredient # PoundsGallons Description 1 155.91 18.13 RhoplexWL-91 Acrylic Emulsion 2 486.36 58.6 Deionized Water 3 105.56 12.27NeoRez R-966 4 3.32 0.39 Diethylene glycol methyl ether 5 1.13 0.12Nuosep 95 Biocide 6 0.74 0.10 Aqueous Ammonia 7 41.7 5.15 8% AcrysolTT615 Rheology Modifier* 8 5.63 0.67 Surfynol 104E Surfactant 9 6.560.75 Dibutyl phthalate 10 — — Aqueous Ammonia 11 31.60 3.81 DeionizedWater *Acrysol TT615 is a commercially available rheology modifier fromRohm & Haas. It is used here as a solution of 215.75 lbs Acrysol TT615in a cosolvent blend comprising 135.1 lbs isopropanol, 424.8 lbsdiethylene glycol methyl ether, 10.0 lbs aqueous ammonia and 14.55 lbswater.

A preferred procedure comprises mixing ingredients #1 through #3together at low speed, premixing ingredients #4 through #9 and then mixtogether with #1-#3 for approximately one hour. Add ingredients #10 and#11 to adjust pH to approximately 8.5 to 9.0 and viscosity to 11000 to17000 cps using a Brookfield LVT with #3 spindle at 6 rpm.

The intermediate from Table 3 becomes the primary ingredient informulating the metallic toner according to the sample formula andprocedure of Table 4:

TABLE 4 Ingredient # PoundsGallons Description 1 629.64 75.09Intermediate from Table 3 2 28.59 3.44 Deionized Water 3 16.70 1.94Water Reducible Acrylic Resin** 4 16.64 2.18 Methoxypropanol 5 1.09 0.13Diethylene glycol methyl ether 6 1.51 0.25 Triethylamine (98.5%) 7 0.650.07 Disperbyk Dispersing Aid 8 52.96 4.07 Stapa Hydralac W 33NLAluminum paste 9 10.52 1.27 Deionized Water 10 22.38 2.70 DeionizedWater 11 73.55 8.86 Deionized Water 12 — — Intermediate from Table 3 **Agraft copolymer of castor oil and acrylic monomers purchased from CCPunder the name XR17-B080-83 believed to be produced according to theprocedures taught in U.S. Pat. No. 3,808,163, incorporated herein byreference.

A preferred procedure for Table 4 is to first mix ingredients #1 and #2at low speed. In a separate vessel, add #3 through #7 at low speed andthen add #8 slowly using good agitation. Mix for about 5 minutes. Add #9and mix until a Hegman grind of about 6 is achieved then add to thefirst vessel containing #1 and #2. Add #10 to wash the sides of thesecond vessel into the first vessel. Add #11 as necessary to adjustviscosity to 1800-3500 cps using a Brookfield LVT #3 spindle at 30 rpmand add #12 to adjust tint strength as desired.

Mica-based toners follow the same procedure used in Table 3; however,the procedure for mixing the mica pigment into the intermediate isgenerally much simpler than that used with metallics. Table 5 shows onesuch preferred procedure:

TABLE 5 Ingredient # PoundsGallons Description 1 704.03 83.96Intermediate from Table 3 2 89.95 10.84 Deionized Water 3 49.77 1.92Afflair 9225 Blue Mica Pigment 4 27.22 3.28 Deionized Water 5 —Intermediate from Table 3

A preferred procedure for mica-based toners is to mix ingredients #1 and#2 and to sift in ingredient #3. Mix at low speed until a Hegman grindof about 6 is attained. Adjust pH using aqeuous ammonia (14% in water)to a value of 8.0 to 9.0. Add #4 to adjust viscosity to 1800-2700 cpsusing a Brookfield LVT #3 spindle at 30 rpm and add #5 to adjust tintstrength as desired.

Using the recipes outlined above, one can formulate a wide variety ofnonmetallic, metallic and mica-based toners. These toners are allcompatible with one another and can be mixed together to preparecustomized basecoat colors as desired.

b. Mixing Clears

The mixing clears described in more detail below are useful incombination with the toners described above to regulate not only thetint strength of the final basecoat but to impart properties to thebasecoat that are particularly suited to the environment under which thebasecoat will be applied and dried. For example, different dryingcharacteristics are desired from the basecoat depending on whether thebasecoat will be baked dry at elevated temperature or whether thebasecoat will be air dried at room temperature. Typical OEM productionlines can use elevated temperature drying. However, due to the presenceof vehicle parts which can melt or otherwise deform, the typical VR shopmust dry the paint layers at much lower temperatures than those used onthe original production line. We have found that depending on the enduse (OEM or VR), two different mixing clears are preferred.

For vehicle refinish applications where lower temperature drying of thecoating is desired, a preferred mixing clear resin component comprisesan aqueous acrylic emulsion resin as the main ingredient, preferably theWL-91 resin commercially available from Rohm & Haas. A preferredcomposition for one such mixing clear is shown in Table 6:

TABLE 6 Ingredient PoundsGallons Description 1 298.47 35.96 DeionizedWater 2 339.99 39.53 WL-91 Acrylic Emulsion 3 46.67 6.10 Methoxypropanol4 0.93 0.10 Nuosep 95 Biocide 5 6.55 0.86 Surfynol 104BC 6 14.38 1.65Dibutyl phthalate 7 1.91 0.25 Aqueous Ammonia 8 62.06 8.39 8% AcrysolTT615 Rheology Modifier*** 9 — — Aqueous Ammonia 10 59.39 7.16 DeionizedWater ***Acrysol TT615 is a commercially available rheology modifierfrom Rohm & Haas. It is used here as a solution of 197.3 lbs AcrysolTT615 in a cosolvent blend comprising 252.5 lbs isopropanol, 259.0 lbsbutoxy ethanol, 10.0 lbs aqueous ammonia and 12.3 lbs water.

A preferred procedure for making this mixing clear is to mix #1 and #2together at low speed. Add ingredients #3 through #8 to #1 and #2 andmix for one hour. Use #9 to adjust pH 8.5 and use #10 to adjustviscosity to 2500-3500 cps using a Brookfield LVT #3 spindle at 30 rpm.

Unlike the mixing clear preferred for lower temperature dryingsituations, in bake dry systems we have found that a mixing clearcomprising a water-dispersible polyurethane resin such as the NeoRezR-966 resin is preferred. Table 7 demonstrates one such preferred mixingclear:

TABLE 7 Ingredient # PoundsGallons Description 1 49.6 6.5 NeoRez R-966 213.9 1.7 Deionized Water 3 0.23 — 14% ammonia in Water 4 0.87 0.10Diethylene glycol methyl ether 5 0.12 — Surfynol 104E 6 1.80 0.20Deionized Water 7 0.94 0.10 Acrysol TT615 Rheology Modifier 8 11.5 1.4Deionized Water

A preferred procedure for making this mixing clear is to premix #2 and#3 and then add to #1 with good agitation. Premix #4 and #5 and add tothe batch. Add #6 to #7 and add to the batch. Add #8 to adjust viscosityto about 2500 cps using a Brookfield LVT #3 spindle at 30 rpm.

Using the above Tables 1 through 7 as representative examples ofpreferred toners and mixing clears, one can formulate waterbornebasecoats having acceptability for use in either OEM or VR applications.By way of example the following teal-colored metallic basecoat can beformulated having particular utility in a vehicle refinish application:

TABLE 8 Ingredient Grams Mixing Clear from Table 6 276.8 Blue Mica Tonerfrom Table 5 226.0 Green Flop Blue Nonmetallic Toner from Table 2 159.6Blue Shade Green Nonmetallic Toner (similar procedure to 88.1 Tables 1and 2 with diff. pigment) Aluminum Metallic Toner from Table 4 69.3Deionized Water 156.8

The above basecoat has a VOC of 2.20 pounds per gallon less water. Itcan be reduced to “ready-to-spray” viscosity with either water or acombination of water with aqueous cosolvent. Conventional siphon and/orHVLP spray guns are typically used for application purposes. Completehiding is usually attained with two or three coats, depending on thecolor.

Optionally included in the basecoat just prior to spraying areingredients which enhance or modify various performance characteristicsof the coating. For example, ambient cure crosslinkers such as aromaticand aliphatic carbodiimide crosslinkers or Dixie Chemical's DCE 358glycidyl ether of sorbitol epoxy crosslinker can be added. Also, highlycrosslinked acrylic microgel particles such as those taught in U.S. Pat.No. 4,377,661 can be added for rheology control. Furthermore,commercially available polyethylene wax dispersions such as Aquacer 840available from Byk Chemie can be added for metal pigment control, ifdesired. Other additives are likewise available and suitable for useherein.

Primer/Basecoat/Clearcoat Combinations

The compositions of this invention are particularly well suited for usein multilayer decorative and protective coatings and composite coatingsas the first layer or basecoat layer over which a second layer orclearcoat layer is applied.

The basecoat compositions of this invention are specifically formulatedto be compatible with commercially existing and available primers,sealers, surfacers and clearcoats. In addition to chemicalcompatibility, overall VOC compliance of the entire system is thedriving force in determining which compositions to use both under andover the present basecoats. For example, the following combinations ofcommercially available compositions from The Sherwin-Williams Company,Cleveland, Ohio. USA with the basecoat composition of this invention(compositions disclosed above which are preferred for use in vehiclerefinish applications) would be expected to be compatible and incompliance with current California VOC regulations:

Primer-Surfacers: Sherwin-Williams Aqua-Fill ™ One Component Primer(Product Number W7-A2250) or Sherwin-Williams Aqua II ™ Two ComponentExpoxy (Product Numbers W8-A2500 and V6-W2503) Primer-Sealers:Sherwin-Williams Sunfire ™ Urethane Primer (Product Number E2-A820) orSherwin-Williams Aqua II ™ Two Component Expoxy (Product Numbers W8-2500and V6-W2501) Clearcoats Sherwin-Williams Ultra 7000 ™ Clearcoat (BoothBake) (Product Number CC-835) or Sherwin-Williams Ultra 7000 ™ Clearcoat(Air Dry) (Product Number CC-830)

What is claimed is:
 1. A method of forming a multilayer coating on asubstrate, said method comprising the steps of: (a) forming a waterbornebasecoat composition comprising the steps of: i) providing a pigmentedtoner composition comprising: water; a polyurethane resin dispersible inwater; a resin selected from the group consisting of water-reducibleresins and aqueous emulsion polymers, produced by a free-radicaladdition polymerization reaction; and at least one pigment; (ii)providing a mixing clear composition comprising a resin selected for aparticular environment under which the basecoat composition is to beapplied to the substrate and dried, said resin being one of an aqueousemulsion polymer produced by a free-radical addition polymerizationreaction and a polyurethane resin dispersible in water; and (iii) mixingthe pigmented toner composition with the mixing clear composition; (b)applying the basecoat composition to the substrate to form a basecoatlayer; (c) providing a clear coat composition; and (d) applying theclear coat composition to the surface of the basecoat layer.
 2. Themethod of claim 1, wherein the polyurethane resin of the pigmented tonercomposition is an aliphatic polyether-polyurethane.
 3. The method ofclaim 1, wherein when the basecoat composition is to be baked dry at anelevated temperature, the resin of the mixing clear composition is thepolyurethane resin dispersible in water, and when the basecoatcomposition is to be air dried at room temperature, the resin of themixing clear composition is the aqueous emulsion polymer produced by afree-radical addition polymerization reaction.
 4. The method of claim 3,wherein the aqueous emulsion polymer of the mixing clear composition isformed from a group of monomers comprising styrene, 2-ethylhexylacrylate, acrylic acid and acrylonitrile.
 5. The method of claim 4,wherein the polyurethane resin of the mixing clear composition comprisesthe reaction product of isophorone diisocyanate, polytetrahydrofuran anddimethylolpropionic acid.
 6. The method of claim 1, wherein in thepigmented toner composition, the resin selected from the groupconsisting of water-reducible resins and aqueous emulsion polymers isproduced by a free-radical polymerization reaction of monomers selectedfrom the group consisting of acrylic monomers, vinyl monomers, preformedpolymers, polymeric intermediates, multifunctional epoxides, melamines,isocyanates, and mixtures thereof.
 7. The method of claim 6, wherein inthe pigmented toner composition, the resin selected from the groupconsisting of water-reducible resins and aqueous emulsion polymers isproduced by a free-radical polymerization reaction of monomers selectedfrom the group consisting of acrylonitrile, methacrylonitrile, hydroxyethyl acrylate and methacrylate, methyl acrylate and methacrylate,hydroxy propyl acrylate and methacrylate, ethyl acrylate andmethacrylate, butyl acrylate and methacrylate, lauryl acrylate andmethacrylate, trimethylol propane triacrylate and trimethacrylate,hexanediol diacrylate, caprolactone modified hydroxy ethyl acrylate,polyethylene oxide acrylate and methacrylate, polypropylene oxideacrylate and methacrylate, allyl alcohol, acrylamide, methacrylamide,vinyl chloride, vinylidene chloride, acrylic acid, methacrylic acid,itaconic acid, maleic acid, fumaric acid, styrene, divinyl benzene,vinyl naphthalene, vinyl toluene, the methyl esters of itaconic, maleicand fumaric acid, and mixtures thereof.
 8. The method of claim 7,wherein in the pigmented toner composition, the resin selected from thegroup consisting of water-reducible resins and aqueous emulsion polymersis produced by a free-radical polymerization reaction of monomerscomprising methyl methacrylate, styrene, butyl acrylate, butylmethacrylate, hydroxy ethyl methacrylate and acrylic acid.
 9. The methodof claim 7, wherein the polyurethane resin of the pigmented tonercomposition comprises the reaction product of isophorone diisocyanate,polytetrahydrofuran and dimethylolpropionic acid.